The electron gun includes a cathode and a control gate, between which a radiofrequency signal to be amplified is applied, this signal modulating the energy of the electron beam. In the interaction space, some of the kinetic energy of the electron beam is converted into electromagnetic-wave form in the resonant cavity.
Multibeam tubes exist. These tubes are known in the literature as multiple beam inductive output tubes (MBIOTs). More precisely, in order to increase the power output from the tube, it is possible to make provision for a plurality of electron beams to interact with a single resonant cavity. The various beams are each generated by one electron gun. The gates of the various guns receive the same radiofrequency signal to be amplified.